Multi-site sensor arrays and related compositions and methods

Abstract

According to some embodiments, sensors of species are provided including multi-site arrays of chemiresistive sensors, which can be based on metal-organic frameworks. Gases, and in some cases liquids, are sensed in certain embodiments.

Description

[0001] MULTI-SITE SENSOR ARRAYS AND RELATED COMPOSITIONS AND METHODS

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 667,338, filed July 3, 2024, and entitled “Multi-Site Sensor Arrays and Related Methods,” which is incorporated herein by reference in its entirety for all purposes.

[0004] GOVERNMENT SPONSORSHIP

[0005] This invention was made with government support under DE-EE0009165 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

[0006] TECHNICAL FIELD

[0007] Multi-site (e.g., pixelated) sensor arrays for detecting substances, including fluids such as gases, via chemiresistance, are generally described.

[0008] BACKGROUND

[0009] Chemiresistive gas sensors, capable of measuring resistance variations triggered by gas reactions, can provide valuable ambient air information and thus enhance the quality of human life. Compared to bulky, expensive, and time-consuming spectroscopic-type gas sensing methods, chemiresistive-type sensing offer advantages in fast, cost-effectiveness, device integrity, and portability, making them suitable for daily use. Early sensors of this type employed metal oxide chemiresistors. The complexity of application environments, including breath analysis, food safety monitoring, and smart farming, further necessitates the development of gas sensor arrays to ensure accurate and reliable detection of multiple gases. To address multiple signals from array devices, various pattern recognition techniques have been developed, ranging from classical methods to current artificial intelligence (Al)-assisted methods such as deep learning and neural networks. These advanced Al techniques can analyze complex and high-dimensional data more effectively, providing enhanced accuracy and reliability in signal interpretation. Given that pattern recognition technology has been successfully applied and commercialized in visual and auditory sensor technologies, which deal with intuitive and low-dimensional signals, it is crucial to identify effective chemiresistor combinations that can enhance pattern recognition in chemical sensor signals as well. SUMMARY

[0010] Sensor arrays for detecting fluids (e.g., gases) and related compositions (e.g., metalorganic framework (MOF)-based compositions) and methods are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0011] According to certain embodiments, a composition is described. In some embodiments, the composition comprises a plurality of metal-organic frameworks, each MOF of the plurality having a formula [MxM’yM”z(Li)(L2)]n, wherein: M, M’, and M” are each independently a metal ion, wherein each of M, M’, and M” are different metal ions; x, y, and z are each independently greater than or equal to 0 and less than or equal to 3, wherein the sum of x, y, and z is 3; Li and L2 each comprise a ligand and Li and L2 can be the same or different; n is greater than or equal to 2; the plurality of MOFs comprises at least two MOFs having different formulas; and at least one MOF has the formula [MxM’yM”z(Li)(L2)]n wherein each of x, y, and z are greater than 0.

[0012] In certain embodiments, a sensor array is described. In some embodiments, the sensor array comprises a plurality of n-type chemiresistors and a plurality of p-type chemiresistors. According to some embodiments, the sensor array is configured such that exposure to an analyte results in: (i) a negative change in electrical resistance of at least a portion of the plurality of n- type chemiresistors; and (ii) a positive change in electrical resistance of at least a portion of the plurality of p-type chemiresistors. In certain embodiments, an output of the sensor array provides a signal pattern unique to a composition of the analyte, the signal pattern comprising a continuous linear baseline where the negative change in electrical resistance and the positive change in electrical resistance cancel each other out.

[0013] According to certain embodiments, a method of sensing an analyte is described. In some embodiments, the method comprises: exposing a sensor array comprising a plurality of chemiresistors to a sample suspected of containing an analyte, wherein the sample comprises a mixture of gases; measuring a change in electrical resistance of at least two chemiresistors of the plurality; outputting a signal pattern based on the change in electrical resistance of the at least two chemiresistors; and determining a composition and a concentration of the analyte, if present, based on the signal pattern.

[0014] According to certain embodiments, a sensor system is described. In some embodiments the system comprises a plurality of chemiresistive sensors interconnected with the system, wherein the system is configured to produce a signal pattern responsive to inputs from at least some of the plurality of chemiresistive sensors, upon exposure to a sample, where the pattern corresponds to at least one species in the sample.

[0015] In some embodiments, at least some of the plurality of chemiresistive sensors comprise a MOF-based sensor composition.

[0016] In certain embodiments, the sample comprises a fluid.

[0017] In some embodiments, the sample comprises a gas.

[0018] According to some embodiments, the system comprises at least 100 sensors or, in other embodiments, at least 500, 1000, 5000, 10,000, 100,000, 250,000, or at least 1,000,000 sensors interconnected with the system.

[0019] In certain embodiments, the system comprises at least 100 sensors or, in other embodiments, at least 500, 1000, 5000, 10,000, 100,000, 250,000, or at least 1,000,000 sensors interconnected with the system, each able to provide an input signal, responsive to the species, which together produce a signal pattern determinative of the species.

[0020] According to some embodiments, the system is driven by process engineering and / or other processing as described herein.

[0021] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0024] FIG. 1 shows a top-view schematic diagram of a sensor array, in accordance with certain embodiments.

[0025] FIGS. 2A-2B show top-view schematic diagrams representing a method of exposing a sensor array to a sample suspected of containing an analyte, in accordance with certain embodiments. FIG. 3A shows an exemplary synthesis of M3(HITP)2 (M = Co, Ni, Cu; HITP = 2,3,6,7,10,11-hexaiminotriphenylene) and CoxNiyCuzHITP2 alloys (x+y+z=3), in accordance with certain embodiments.

[0026] FIG. 3B shows a phase diagram of a ternary HITP MOFs system, in accordance with certain embodiments.

[0027] FIG. 3C shows X-ray diffraction (XRD) patterns of Ma(HITP)2 (M = Co, Ni, Cu), in accordance with certain embodiments.

[0028] FIG. 3D shows integration of the (100) plane peak position for a MOF ternary system, in accordance with certain embodiments.

[0029] FIG. 4A shows schematics of one-chip sensor array devices, and sensing mechanisms of chemiresistors, in accordance with certain embodiments.

[0030] FIG. 4B shows a response pattern of a single MOFs system, in accordance with certain embodiments.

[0031] FIG. 4C shows a response pattern of a binary MOF alloy system, in accordance with certain embodiments.

[0032] FIG. 4D shows a response pattern of a ternary MOF alloy system, with a comparison to a fingerprint recognition technique, in accordance with certain embodiments.

[0033] FIG. 5A shows a fingerprint pattern of methane at a concentration of 2000 ppm, in accordance with certain embodiments.

[0034] FIG. 5B shows a fingerprint pattern of methane at 1000 ppm, in accordance with certain embodiments.

[0035] FIG. 5C shows a fingerprint pattern of methane at 500 ppm, in accordance with certain embodiments.

[0036] FIG. 5D shows a fingerprint pattern of methane at 250 ppm, in accordance with certain embodiments.

[0037] FIGS. 6A-6K show fingerprint patterns of various airborne chemicals, in accordance with certain embodiments.

[0038] FIG. 7 shows a calculation result of decomposing gas response patterns for a H2 + CH4 mixture into the sum of the H2 pattern and the CH4 pattern at different concentration ratios.

[0039] DETAILED DESCRIPTION

[0040] Multi-site sensor systems or arrays which together can produce a signal (e.g., a fingerprint signal) indicative of an analyte or other species such as a gas are described herein, along with certain metal-organic frameworks (MOFs), and methods that can be related to either or both. In some embodiments, sensors and / or arrays can be MOF-based. As used herein, the term “metal-organic framework” (or “MOF”) is given its ordinary meaning in the field of chemistry and refers to a class of porous polymers consisting of metal ions or metal clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures. In certain embodiments, MOFs are characterized by high surface area, tunable pore size, and structural versatility, making them suitable for applications such as fluid (e.g., gas) storage, fluid (e.g., gas) separation, and / or fluid (e.g., gas) sensing.

[0041] According to certain embodiments, MOF-based compositions are described. A MOF- based composition may comprise a plurality of MOFs. The plurality of MOFs may comprise single metallic MOFs, such as a first MOF having a first metal ion, a second MOF having a second metal ion different from the first metal ion, and a third MOF having a third metal ion different from the first metal ion and the second metal ion. The plurality of MOFs may further comprise MOFs having various ratios of the first, second, and third metal ions, including, e.g., bimetallic MOFs having two of the three metal ions in defined proportions and bimetallic MOFs incorporating all three metal ions in defined proportions.

[0042] The MOF-based compositions may be configured to detect a plurality of target analytes. In certain embodiments, each MOF of the plurality is at least partially porous such that each MOF is configured to interact with (e.g., adsorb) one or more target analytes, for example, within one or more pores of the MOF. In some embodiments, each MOF of the plurality is electrically conductive such that each MOF exhibits a detectable change upon interacting with (e.g., adsorbing) the one or more target analytes. For example, in some embodiments, each MOF of the plurality is a chemiresistor that is configured to exhibit a detectable change in electrical resistance upon interacting with the one or more target analytes. Adjusting the proportions of each metal ion in each MOF (e.g., from single metallic MOFs, to bimetallic MOFs, to trimetallic MOFs) advantageously provides a composition suitable for sensing a wide variety of target analytes as each MOF of the plurality exhibits an individual signal (e.g., a detectable change in electrical resistance) upon exposure to each target analyte. Each individual signal of each MOF of the plurality may collectively form a signal pattern (e.g., a fingerprint) that is unique to the composition of individual target analytes.

[0043] According to some embodiments, a sensor array is described. The sensor array may comprise a plurality of interconnected chemiresistors. For example, the sensor array may comprise a plurality of n-type chemiresistors (e.g., MOF-based n-type chemiresistors) and a plurality of p-type chemiresistors (e.g., MOF-based p-type chemiresistors). In some embodiments, exposing the sensor array to a target analyte results in: (i) a negative change in electrical resistance of at least a portion of the plurality of n-type chemiresistors; and (ii) a positive change in electrical resistance of at least a portion of the plurality of p-type chemiresistors.

[0044] An output of the sensor array may provide a signal pattern comprising one or more signal areas corresponding to a negative change in electrical resistance (e.g., of at least a first portion of the n-type chemiresistors) and / or one or more signal areas corresponding to a positive change in electrical resistance (e.g., of at least a first portion of the p-type chemiresistors). The signal pattern may further comprise a continuous linear baseline where a negative change in electrical resistance (e.g., of at least a second portion of the n-type chemiresistors) and a positive change in electrical resistance (e.g., of at least a second portion of the p-type chemiresistors) cancel each other out. In certain embodiments, the signal pattern (e.g., the continuous linear baseline) is unique to the composition of the target analyte such that different target analytes produce different signal patterns (e.g., different continuous linear baselines). The continuous linear baseline may, in certain embodiments, be independent of the concentration of the target analyte. Advantageously, the signal pattern (e.g., the continuous linear baseline) may be used to detect the composition of the target analyte.

[0045] The signal pattern may further comprise one or more contours having a signal intensity value corresponding to the concentration of the target analyte. For example, in certain embodiments, a signal area corresponding to a negative change in electrical resistance (e.g., of at least a portion of n-type chemiresistors) and / or a signal area corresponding to a positive change in electrical resistance (e.g., of at least a portion of p-type chemiresistors) comprises at least one contour having a signal intensity value that is directly proportional to the concentration of the target analyte. The signal pattern may therefore advantageously be used to detect both the composition and the concentration of individual target analytes, including when the target analyte is present in a sample comprising a mixture of substances.

[0046] Methods of sensing (e.g., detecting) target analytes are also described. In some embodiments, a method comprises exposing a sensor array comprising a plurality of chemiresistors (e.g., MOF-based chemiresistors) to a sample suspected of containing a target analyte. In certain embodiments, for example, the sample may comprise a mixture of fluids (e.g., gases and / or liquids). The method may further comprise measuring a change in electrical resistance (e.g., a negative change in electrical resistance and a positive change in electrical resistance) of at least two chemiresistors of the plurality, outputting a signal pattern based on the change in electrical resistance of the at least two chemiresistors, and determining a composition and / or concentration of the target analyte, if present, based on the signal pattern. In certain embodiments, the method comprises measuring a change in electrical resistance of each chemiresistor of the plurality, outputting a signal pattern based on the change in electrical resistance of each chemiresistor of the plurality, and determining a composition and / or concentration of the target analyte, if present, based on the signal pattern.

[0047] The compositions, sensors, and methods described herein may be used in any of a variety of suitable applications, including, but not limited to, environmental monitoring, industrial safety, medical diagnostics, breath analysis, automative and transportation, agriculture and food safety monitoring, and / or smart farming. Other applications for detecting one or more fluids (e.g., gases) are also possible.

[0048] According to certain embodiments, a composition (e.g., a MOF-based composition) is described. In some embodiments, the composition comprises a plurality of MOFs. According to certain embodiments, each MOF of the plurality has Formula (I) shown below.

[0049] [MxM’yM”z(Li)(L2)]n (I)

[0050] In some embodiments, M, M’, and M” in Formula (I) are each independently a metal ion. In certain embodiments, each of M, M’, and M” are different metal ions. For example, in some embodiments, M is a first metal ion, M’ is a second metal ion that is different from the first metal ion, and M” is a third metal ion that is different from the first metal ion and the second metal ion.

[0051] M in Formula (I) may comprise any of a variety of suitable metal ions. In some embodiments, M comprises a transition metal ion. In certain embodiments, M comprises a cobalt (Co) metal ion (e.g., Co2+, Co3+), a nickel (Ni) metal ion (e.g., Ni2+), a copper (Cu) metal ion (e.g., Cu+, Cu2+), a silver (Ag) metal ion (e.g., Ag+), a gold (Au) metal ion (e.g., Au+), a magnesium (Mg) metal ion (e.g., Mg2+), a manganese (Mn) metal ion (e.g., Mn2+, Mn3+), an iron (Fe) metal ion (e.g., Fe2+, Fe3+), a palladium (Pd) metal ion (e.g., Pd2+), a platinum (Pt) metal ion (e.g., Pt2+), a ruthenium (Ru) metal ion (e.g., Ru2+), a cadmium (Cd) metal ion (e.g., Cd2+), a zinc (Zn) metal ion (e.g., Zn2+), a lead (Pb) metal ion (Pb2+), a mercury (Hg) metal ion (e.g., Hg2+), a vanadium (V) metal ion (e.g., V2+, V3+), a chromium (Cr) metal ion (e.g., Cr2+, Cr3+), a titanium (Ti) metal ion (e.g., Ti3+), a scandium (Sc) metal ion (e.g., Sc3+), an aluminum (Al) metal ion (e.g., Al3+), an indium (In) metal ion (e.g., In3+), a gallium (Ga) metal ion (e.g., Ga3+), a lanthanum (La) metal ion (e.g., La3+), or a neodymium (Nd) metal ion (e.g., Nd3+). Other metal ions are also possible for M.

[0052] M’ in Formula (I) may comprise any of a variety of suitable metal ions. In some embodiments, M’ comprises a transition metal ion. In certain embodiments, M’ comprises a Co metal ion (e.g., Co2+, Co3+), a Ni metal ion (e.g., Ni2+), a Cu metal ion (e.g., Cu+, Cu2+), a Ag metal ion (e.g., Ag+), a Au metal ion (e.g., Au+), a Mg metal ion (e.g., Mg2+), a Mn metal ion (e.g., Mn2+, Mn3+), an Fe metal ion (e.g., Fe2+, Fe3+), a Pd metal ion (e.g., Pd2+), a Pt metal ion (e.g., Pt2+), a Ru metal ion (e.g., Ru2+), a Cd metal ion (e.g., Cd2+), a Zn metal ion (e.g., Zn2+), a Pb metal ion (Pb2+), a Hg metal ion (e.g., Hg2+), a V metal ion (e.g., V2+, V3+), a Cr metal ion (e.g., Cr2+, Cr3+), a Ti metal ion (e.g., Ti3+), a Sc metal ion (e.g., Sc3+), an Al metal ion (e.g., Al3+), an In metal ion (e.g., In3+), a Ga metal ion (e.g., Ga3+), a La metal ion (e.g., La3+), or a Nd metal ion (e.g., Nd3+). Other metal ions are also possible for M’.

[0053] M” in Formula (I) may comprise any of a variety of suitable metal ions. In some embodiments, M” comprises a transition metal ion. In certain embodiments, M” comprises a Co metal ion (e.g., Co2+, Co3+), a Ni metal ion (e.g., Ni2+), a Cu metal ion (e.g., Cu+, Cu2+), a Ag metal ion (e.g., Ag+), a Au metal ion (e.g., Au+), a Mg metal ion (e.g., Mg2+), a Mn metal ion (e.g., Mn2+, Mn3+), an Fe metal ion (e.g., Fe2+, Fe3+), a Pd metal ion (e.g., Pd2+), a Pt metal ion (e.g., Pt2+), a Ru metal ion (e.g., Ru2+), a Cd metal ion (e.g., Cd2+), a Zn metal ion (e.g., Zn2+), a Pb metal ion (Pb2+), a Hg metal ion (e.g., Hg2+), a V metal ion (e.g., V2+, V3+), a Cr metal ion (e.g., Cr2+, Cr3+), a Ti metal ion (e.g., Ti3+), a Sc metal ion (e.g., Sc3+), an Al metal ion (e.g., Al3+), an In metal ion (e.g., In3+), a Ga metal ion (e.g., Ga3+), a La metal ion (e.g., La3+), or a Nd metal ion (e.g., Nd3+). Other metal ions are also possible for M”.

[0054] According to some embodiments, M, M’, and M” in Formula (I) are each independently selected from the group consisting of a Co metal ion (e.g., Co2+, Co3+), a Ni metal ion (e.g., Ni2+), and a Cu metal ion (e.g., Cu+, Cu2+). In certain embodiments, M, M’, and M” are each independently selected from the group consisting of a Co metal ion (e.g., Co2+, Co3+), a Ni metal ion (e.g., Ni2+), and a Cu metal ion (e.g., Cu+, Cu2+), provided that each of M, M’, and M” are different metal ions.

[0055] According to certain embodiments, x, y, and z in Formula (I) are each independently greater than or equal to 0 and less than or equal to 3, wherein the sum of x, y, and z is 3.

[0056] The value of x in Formula (I) may be any of a variety of suitable values. In some embodiments, the value of x is greater than or equal to 0, greater than or equal to 0.1, greater than or equal to 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, greater than or equal to 0.9, greater than or equal to 1, greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.4, greater than or equal to 1.5, greater than or equal to 1.6, greater than or equal to 1.7, greater than or equal to 1.8, greater than or equal to 1.9, greater than or equal to 2, greater than or equal to 2.1, greater than or equal to 2.2, greater than or equal to 2.3, greater than or equal to 2.4, greater than or equal to 2.5, greater than or equal to 2.6, greater than or equal to 2.7, greater than or equal to 2.8, or greater than or equal to 2.9. In some embodiments, the value of x is less than or equal to 3.0, less than or equal to 2.9, less than or equal to 2.8, less than or equal to 2.7, less than or equal to 2.6, less than or equal to 2.5, less than or equal to 2.4, less than or equal to 2.3, less than or equal to 2.2, less than or equal to 2.1, less than or equal to 2, less than or equal to 1.9, less than or equal to 1.8, less than or equal to 1.7, less than or equal to 1.6, less than or equal to 1.5, less than or equal to 1.4, less than or equal to 1.3, less than or equal to 1.2, less than or equal to 1.1, less than or equal to 1, less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1. Combinations of the above recited ranges are possible (e.g., the value of x is greater than or equal to 0 and less than or equal to 3, the value of x is greater than or equal to 1 and less than or equal to 2).

[0057] The value of y in Formula (I) may be any of a variety of suitable values. In some embodiments, the value of y is greater than or equal to 0, greater than or equal to 0.1, greater than or equal to 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, greater than or equal to 0.9, greater than or equal to 1, greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.4, greater than or equal to 1.5, greater than or equal to 1.6, greater than or equal to 1.7, greater than or equal to 1.8, greater than or equal to 1.9, greater than or equal to 2, greater than or equal to 2.1, greater than or equal to 2.2, greater than or equal to 2.3, greater than or equal to 2.4, greater than or equal to 2.5, greater than or equal to 2.6, greater than or equal to 2.7, greater than or equal to 2.8, or greater than or equal to 2.9. In some embodiments, the value of y is less than or equal to 3.0, less than or equal to 2.9, less than or equal to 2.8, less than or equal to 2.7, less than or equal to 2.6, less than or equal to 2.5, less than or equal to 2.4, less than or equal to 2.3, less than or equal to 2.2, less than or equal to 2.1, less than or equal to 2, less than or equal to 1.9, less than or equal to 1.8, less than or equal to 1.7, less than or equal to 1.6, less than or equal to 1.5, less than or equal to 1.4, less than or equal to 1.3, less than or equal to 1.2, less than or equal to 1.1, less than or equal to 1, less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1. Combinations of the above recited ranges are possible (e.g., the value of y is greater than or equal to 0 and less than or equal to 3, the value of y is greater than or equal to 1 and less than or equal to 2). The value of z in Formula (I) may be any of a variety of suitable values. In some embodiments, the value of z is greater than or equal to 0, greater than or equal to 0.1, greater than or equal to 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, greater than or equal to 0.9, greater than or equal to 1, greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.4, greater than or equal to 1.5, greater than or equal to 1.6, greater than or equal to 1.7, greater than or equal to 1.8, greater than or equal to 1.9, greater than or equal to 2, greater than or equal to 2.1, greater than or equal to 2.2, greater than or equal to 2.3, greater than or equal to 2.4, greater than or equal to 2.5, greater than or equal to 2.6, greater than or equal to 2.7, greater than or equal to 2.8, or greater than or equal to 2.9. In some embodiments, the value of z is less than or equal to 3.0, less than or equal to 2.9, less than or equal to 2.8, less than or equal to 2.7, less than or equal to 2.6, less than or equal to 2.5, less than or equal to 2.4, less than or equal to 2.3, less than or equal to 2.2, less than or equal to 2.1, less than or equal to 2, less than or equal to 1.9, less than or equal to 1.8, less than or equal to 1.7, less than or equal to 1.6, less than or equal to 1.5, less than or equal to 1.4, less than or equal to 1.3, less than or equal to 1.2, less than or equal to 1.1, less than or equal to 1, less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1. Combinations of the above recited ranges are possible (e.g., the value of z is greater than or equal to 0 and less than or equal to 3, the value of z is greater than or equal to 1 and less than or equal to 2).

[0058] In certain embodiments, Li and L2 in Formula (I) each comprise a ligand. In certain embodiments, Li and L2 can be the same or different. According to some embodiments, Li and / or L2 comprise a monodentate ligand. For example, in some embodiments, Li and / or L2 comprise a ligand that coordinates to a metal ion through one coordinate bond. In certain embodiments, Li and / or L2 comprise a multidentate ligand (e.g., a bidentate ligand, a tridentate ligand, a tetradentate ligand, etc.). In certain embodiments, for example, Li and / or L2 comprise a ligand that coordinates to one or more metal ions through multiple coordinate bonds.

[0059] According to some embodiments, the multidentate ligand is a ligand comprising at least two sets of ortho-diimine groups arranged about an organic core. In certain embodiments, for example, the multidentate ligand comprises at least two sets ortho-diimine groups arranged about an organic core, three sets of ortho-diimine groups arranged about an organic core, four sets of ortho-diimine groups arranged about an organic core, etc. In certain non-limiting embodiments, the ortho-diimine groups are ortho-phenylenediimine groups. The organic core may be any of a variety of suitable organic cores. In some embodiments, the organic core is aromatic. Generally, the organic core may comprise a rigid structure formed from one or more fused aryl and / or heteroaryl rings. In some embodiments, for example, the organic core comprises one or more benzyl, thiophenyl, carbazolyl, pyrrolyl, indolyl, and / or furanyl rings.

[0060] In some embodiments, the multidentate ligand comprising at least two sets of orthodiimine groups arranged about an organic core comprises the structure shown below in Formula (ID- (ID, wherein: n is 1, 2, or 3, and

[0061] C represents one or more bonds formed between ring A and each ring B.

[0062] In some embodiments, the multidentate ligand comprises the structure: wherein: each R1is the same or different and is selected from the group consisting of hydrogen, -

[0063] NO2, -R’, -F, -Cl, -Br, -I, -CN, -NC, -SO3R’, -SO3H, -OR’, -OH, -SR’, -SH, -PO3R’, -

[0064] PO3H, -CF3, -NR’ 2, -NHR’, and -NH2, and each R’ is the same or different and is optionally substituted alkyl or optionally substituted aryl.

[0065] In some embodiments, the multidentate ligand comprises the structure:

[0066] In certain non-limiting embodiments, the multidentate ligand is 2,3,6,7,10,11- hexaiminotriphenylene. Other ligands are also possible.

[0067] Examples of suitable ligands are described in further detail in International Patent Application No. PCT / US2015 / 029503, filed May 6, 2015, and entitled “Compositions and Methods Comprising Conductive Metal Organic Frameworks and Uses Thereof’, which is incorporated herein by reference in its entirety.

[0068] The value of “n” in Formula (I) may be any of a variety of suitable values. In certain embodiments, for example, the value of n is greater than or equal to 5, greater than or equal to 10, greater than or equal to 50, greater than or equal to 100, greater than or equal to 500, greater than or equal to 1,000, greater than or equal to 5,000, greater than or equal to 10,000, greater than or equal to 50,000, greater than or equal to 100,000, greater than or equal to 500,000, greater than or equal to 1,000,000, greater than or equal to 5,000,000, greater than or equal to 10,000,000, greater than or equal to 50,000,000, greater than or equal to 100,000,000, greater than or equal to 500,000,000, or greater. In some embodiments, the value of n is less than or equal to 1,000,000,000, less than equal to 500,000,000, less than or equal to 100,000,000, less than or equal to 50,000,000, less than or equal to 10,000,000, less than or equal to 5,000,000, less than or equal to 1,000,000, less than or equal to 500,000, less than or equal to 100,000, less than or equal to 50,000, less than or equal to 10,000, less than or equal to 5,000, less than or equal to 1,000, less than or equal to 500, less than or equal to 100, less than or equal to 50, or less than or equal to 10. Combinations of the above recited ranges are possible (e.g., the value of n is greater than or equal to 5 and less than or equal to 1,000,000,000, the value of n is greater than or equal to 10,000 and less than or equal to 50,000). Other ranges are also possible. According to certain embodiments, the value of n is determined by measuring the physical dimensions of a single crystal of the MOF and back calculating the total number of unit cells within the single crystal based on the lattice parameters of the single crystal.

[0069] In certain embodiments, the value of n may be tunable based on the size of the physical dimensions of the single crystal. The MOF single crystal may have any of a variety of suitable maximum characteristic dimensions (e.g., maximum widths and / or maximum lengths). For example, in some embodiments, the MOF single crystal has a maximum characteristic dimension greater than or equal to 1 nm, greater than or equal to 5 nm, greater than or equal to 10 nm, greater than or equal to 50 nm, greater than or equal to 100 nm, greater than or equal to 500 nm, greater than or equal 1 micrometer, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 50 micrometers, or greater. In certain embodiments, the MOF single crystal has a maximum characteristic dimension less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 1 micrometer, less than or equal to 500 nm, less than or equal to 100 nm, less than or equal to 50 nm, less than or equal to 10 nm, or less than or equal to 5 nm. Combinations of the above recited ranges are also possible (e.g., the MOF single crystal has a maximum characteristic dimension greater than or equal to 1 nm and less than or equal to 100 micrometers, the MOF single crystal has a maximum characteristic dimension greater than or equal to 100 nm and less than or equal to 1 micrometer). Other ranges are also possible.

[0070] In certain embodiments, each of the metal ions (e.g., M, M’, and / or M” in Formula (I)) are coordinated with at least one ligand (e.g., Li and / or L2 in Formula (I)). According to some embodiments, for example, each of the metal ions are coordinated with two ligands, and each of those ligands are individually coordinated with three metal ions.

[0071] According to certain embodiments, a MOF of Formula (I) is synthesized by exposing one or more metal ions to one or more ligand precursors. According to some embodiments, the one or more metal ions are provided as one or more metal salts. In certain embodiments, the one or more ligand precursors comprise at least two sets of ortho-diamine groups arranged about an organic core. In some embodiments, the exposing is performed in solution. In certain embodiments, the exposing is performed in the presence of an oxidant and / or a base. In some embodiments, the exposing is performed with stirring and / or heating. According to some embodiments, during the exposing, the diamine groups of the one or more ligand precursors are oxidized into diimine groups, which coordinate with the one or more metal ions of the one or more metal salts. In certain embodiments, for example, the one or more ligand precursors comprise at least two sets of ortho-phenylenediamine groups arranged about an organic core, and during the exposing, the ortho-phenylenediamine groups are oxidized into orthophenylenediimine groups, which coordinate with the one or more metal ions of the one or more metal salts.

[0072] Various conditions that may be used to synthesize a MOF of Formula (I) are described in further detail in International Patent Application No. PCT / US2015 / 029503, filed May 6, 2015, and entitled “Compositions and Methods Comprising Conductive Metal Organic Frameworks and Uses Thereof’, which is incorporated herein by reference in its entirety.

[0073] According to some embodiments, the plurality of MOFs comprises at least two MOFs having different formulas (e.g., two different formulas of Formula (I)). In certain embodiments, each MOF of the plurality has a different formula (e.g., a different formula of Formula (I)).

[0074] According to some embodiments, the plurality of MOFs comprises at least one bimetallic MOF. For example, in some embodiments, the plurality of MOFs comprises at least one MOF having the formula [MxM’yM”z(Li)(L2)]n, wherein M, M’, and M” are different metal ions and wherein each of x, y, and z are greater than 0. In certain embodiments, at least one MOF of the plurality has the formula [MxM’yM”z(Li)(L2)]n, wherein, M, M’, and M” are different metal ions, x is greater than 0 and less than 3, y is greater than 0 and less than 3, z is greater than 0 and less than 3, and the sum of x, y, and z is 3.

[0075] In some embodiments, the plurality of MOFs comprises at least one bimetallic MOF. For example, in some embodiments, the plurality of MOFs comprises at least one MOF having the formula [MxM’yM”z(Li)(L2)]n, wherein M, M’, and M” are different metal ions and two of x, y, and / or z are greater than 0, provided that one of x, y, and / or z is 0. In certain embodiments, at least one MOF of the plurality has the formula [MxM’y(Li)(L2)]n, wherein M and M’ are different metal ions, x is greater than 0 and less than 3, y is greater than 0 and less than 3, and the sum of x, y, and z is 3. In some embodiments, at least one MOF of the plurality has the formula [MxM”z(Li)(L2)]n, wherein M and M” are different metal ions, x is greater than 0 and less than 3, z is greater than 0 and less than 3, and the sum of x and z is 3. In certain embodiments, at least one MOF of the plurality has the formula [M’yM”z(Li)(L2) ]n, wherein M’ and M” are different metal ions, y is greater than 0 and less than 3, z is greater than 0 and less than 3, and the sum of y and z is 3.

[0076] According to certain embodiments, the plurality of MOFs comprises at least one single metallic MOF. In certain embodiments wherein M, M’, and M” are different metal ions, for example, the plurality of MOFs comprises at least one MOF having the formula [M3(Li)(L2)]n, at least one MOF having the formula [M’3(Li)(L2)]n, and / or at least one MOF having the formula [M”3(Li)(L2)]n.

[0077] According to some embodiments, at least one MOF of the plurality (e.g., each MOF of the plurality) is electrically conductive. At least one MOF of the plurality (e.g., each MOF of the plurality) may have any of a variety of suitable electrical conductivities. In certain embodiments, for example, at least one MOF of the plurality has an electrical conductivity greater than or equal to IO'10S / m, greater than or equal to 10'9S / m, greater than or equal to 10'8S / m, greater than or equal to 10'7S / m, greater than or equal to 10'6S / m, greater than or equal to 10'5S / m, greater than or equal to 10'4S / m, greater than or equal to 10'3S / m, greater than or equal to 10'2S / m, greater than or equal to 10'1S / m, greater than or equal to 1 S / m, greater than or equal to 10 S / m, greater than or equal to 102S / m, greater than or equal to 103S / m, or greater. In some embodiments, at least one MOF of the plurality has an electrical conductivity less than or equal to 104S / m, less than or equal to 103S / m, less than or equal to 102S / m, less than or equal to 10 S / m, less than or equal to 1 S / m, less than or equal to 10'1S / m, less than or equal to 10'2S / m, less than or equal to 10'3S / m, less than or equal to IO"4S / m, less than or equal to 10'5S / m, less than or equal to 10'6S / m, less than or equal to 10'7S / m, less than or equal to 10'8S / m, or less than or equal to 10'9S / m. Combinations of the above recited ranges are also possible (e.g., at least one MOF of the plurality has an electrical conductivity greater than or equal to 10’10S / m and less than or equal to 104S / m, at least one MOF of the plurality has an electrical conductivity greater than or equal to IO"4S / m and less than or equal to 10'3S / m). Other ranges are also possible.

[0078] According to certain embodiments, the electrical conductivity of a MOF is determined using a four-point probe method. A powdered composition of the MOF may be compressed into a pellet and measured using the four-point probe method, or a single crystal of the MOF may be measured using the four-point probe method.

[0079] In certain embodiments, at least one MOF of the plurality (e.g., each MOF of the plurality) is at least partially porous. An at least partially porous MOF advantageously allows the MOF to absorb one or more gases (e.g., within one or more pores of the MOF). At least one MOF of the plurality (e.g., each MOF of the plurality) may have any of a variety of suitable porosities. In some embodiments, for example, at least one MOF of the plurality has a Brunauer-Emmett- Teller (BET) surface area greater than or equal to 500 m2 / g, greater than or equal to 1000 m2 / g, greater than or equal to 1500 m2 / g, greater than or equal to 2000 m2 / g, or greater than or equal to 2500 m2 / g. In some embodiments, at least one MOF of the plurality has a BET surface area less than or equal to 3000 m2 / g, less than or equal to 2500 m2 / g, less than or equal to 2000 m2 / g, less than or equal to 1500 m2 / g, or less than or equal to 1000 m2 / g. Combinations of the above recited ranges are also possible (e.g., at least one MOF of the plurality has a BET surface area greater than or equal to 500 m2 / g and less than or equal to 3000 m2 / g, at least one MOF of the plurality has a BET surface area greater than or equal to 1500 m2 / g and less than or equal to 2000 m2 / g). Other ranges are also possible.

[0080] According to certain embodiments, the BET surface area of a MOF is determined by subjecting a powdered composition of the MOF to vacuum heat treatment below its decomposition temperature to remove any undesired solvent molecules from the pores of the MOF and measuring the surface area using a BET analyzer.

[0081] The plurality of MOFs may comprise any of a variety of suitable number of MOFs. In certain embodiments, for example, the plurality of MOFs comprises greater than 2 MOFs, greater than or equal to 5 MOFs, greater than or equal to 10 MOFs, greater than or equal 20 MOFs, greater than or equal to 50 MOFs, greater than or equal to 100 MOFs, greater than or equal to 200 MOFs, greater than or equal to 500 MOFs, greater than or equal to 1,000 MOFs, greater than or equal to 5,000 MOFs, greater than or equal to 10,000 MOFs, greater than or equal to 50,000 MOFs, greater than or equal to 100,000 MOFs, greater than or equal to 250,000 MOFs, greater than or equal to 500,000 MOFs, greater than or equal to 1,000,000 MOFs, or more. In some embodiments, the plurality of MOFs comprises less than or equal to 1,000,000 MOFs, less than or equal to 500,000 MOFs, less than or equal to 250,000 MOFs, less than or equal to 100,000 MOFs, less than or equal to 50,000 MOFs, less than or equal to 10,000 MOFs, less than or equal to 5,000 MOFs, less than or equal to 1,000 MOFs, less than or equal to 500 MOFs, less than or equal to 200 MOFs, less than or equal to 100 MOFs, less than or equal to 50 MOFs, less than or equal to 20 MOFs, less than or equal to 10 MOFs, or less than or equal to 5 MOFs. Combinations of the above recited ranges are possible (e.g., the plurality of MOFs comprises greater than or equal to 2 MOFs and less than or equal to 1,000,000 MOFs, the plurality of MOFs comprises greater than or equal to 500 MOFs and less than or equal to 1,000 MOFs). Other ranges are also possible.

[0082] According to certain embodiments, a sensor array is described. FIG. 1 shows a top-view schematic diagram of sensor array 102, in accordance with certain embodiments. In certain embodiments, the sensor array comprises a plurality of sensors (e.g., individual sensors configured in an array). For example, referring to FIG. 1, sensor array 102 comprises a plurality of individual sensors 106 (e.g., sensors 106a-106r) configured in an array. The sensors may, in some embodiments, be or comprise a plurality of chemiresistors (e.g., individual chemiresistors configured in an array). Referring to FIG. 1, for example, sensors 106 may be chemiresistors. In other embodiments, sensors 106 are sensing materials comprising a chemiresistor. As used herein, the term “chemiresistor” is given its ordinary meaning in the field of chemistry and refers to a chemical sensor whose electrical resistance changes in response to exposure to a target analyte. In certain embodiments, the sensing mechanism of a chemiresistor relies on an interaction between the target analyte and the chemiresistor (or an interaction between the target analyte and a sensing material comprising the chemiresistor), which induces a measurable change in a conductive property of the chemiresistor.

[0083] According to some embodiments, the plurality of sensors are positioned on a surface of a substrate. For example, referring to FIG. 1, sensors 106 are positioned on a surface of substrate 104. Suitable substrates are described herein in greater detail.

[0084] In some embodiments, at least a portion of the sensors (e.g., chemiresistors) are or comprise n-type chemiresistors. Referring, for example, to FIG. 1, at least a portion of sensors 106 (e.g., chemiresistors) are or comprise n-type chemiresistors. As used herein, the term “n- type chemiresistor” is given its ordinary meaning in the art and refers to a chemiresistive sensor that conducts electricity via electrons as the majority charge carrier. In some embodiments, upon exposure to a target analyte, interactions between the target analyte and the n-type chemiresistor (e.g., at a surface of the n-type chemiresistor, within one or more pores of the n-type chemiresistor) result in a change in electron concentration of the n-type chemiresistor, thereby altering the electrical resistance of the n-type chemiresistor. In certain embodiments wherein the target analyte comprises a reducing species, the target analyte may donate electrons to the n-type chemiresistor, which results in an increase in the electron concentration of the n-type chemiresistor, an increase in the electrical conductivity of the n-type chemiresistor, and a decrease in the electrical resistance of the n-type chemiresistor. In other embodiments wherein the target analyte comprises an oxidizing species, the target analyte may accept electrons from the n-type chemiresistor, which results in a decrease in the electron concentration of the n-type chemiresistor, a decrease in the electrical conductivity of the n-type chemiresistor, and an increase in the electrical resistance of the n-type chemiresistor.

[0085] According to some embodiments, at least a portion of the sensors (e.g., chemiresistors) are or comprise p-type chemiresistors. For example, referring to FIG. 1, at least a portion of sensors 106 (e.g., chemiresistors) are or comprise p-type chemiresistors. The term “p-type chemiresistor”, as used herein, is given its ordinary meaning in the art and refers to a chemiresistive sensor that conducts electricity via holes as the majority charge carrier. As used herein, the term “hole” refers to the absence of an electron in a valence band of the chemiresistor. In certain embodiments, upon exposure to a target analyte, interactions between the target analyte and the p-type chemiresistor (e.g., at a surface of the p-type chemiresistor, within one or more pores of the p-type chemiresistor) result in a change in hole concentration of the p-type chemiresistor, thereby altering the electrical resistance of the p-type chemiresistor. In some embodiments wherein the target analyte comprises a reducing species, the target analyte may donate electrons to the p-type chemiresistor, which results in a decrease in the hole concentration of the p-type chemiresistor, a decrease in the electrical conductivity of the p-type chemiresistor, and an increase in the electrical resistance of the p-type chemiresistor. In other embodiments wherein the target analyte comprises an oxidizing species, the target analyte may accept electrons from the p-type chemiresistor, which results in an increase in the hole concentration of the p-type chemiresistor, an increase in the electrical conductivity of the p-type chemiresistor, and a decrease in the electrical resistance of the p-type chemiresistor.

[0086] According to certain embodiments, a first portion of the sensors (e.g., chemiresistors) are or comprise n-type chemiresistors, and a second portion of the sensors (e.g., chemiresistors) different from the first portion are or comprise p-type chemiresistors. In certain embodiments, the number of sensors in the first portion is substantially equal to the number of sensors in the second portion. For example, in some embodiments, the number of n-type chemiresistors and the number of p-type chemiresistors in the sensor array are substantially equal (e.g., the number of n-type chemiresistors and the number of p-type chemiresistors are equal, the number of n-type chemiresistors and the number of p-type chemiresistors differ by no more than 10, no more than 5, no more than 4, no more than 3, no more than 2, or no more than 1).

[0087] In some embodiments, the sensors (e.g., chemiresistors) are positioned on a surface of a substrate such that the n-type chemiresistors and the p-type chemiresistors are in an alternating arrangement. For example, referring to a non-limiting embodiments shown in FIG. 1, sensors 106a- 106r are positioned on a surface of substrate 104 such that sensors 106a, 106c, 106e, 106g, 106i, 106k, 106m, 106o, and 106q are n-type chemiresistors and sensors 106b, 106d, 106f, 106h, 106j, 1061, 106n, 106p, and 106r are p-type chemiresistors (or vice versa, i.e., such that sensors 106a, 106c, 106e, 106g, 106i, 106k, 106m, 106o, and 106q are p-type chemiresistors and sensors 106b, 106d, 106f, 106h, 106j, 1061, 106n, 106p, and 106r are n-type chemiresistors). In other embodiments, the sensors (e.g., chemiresistors) are positioned on a surface of a substrate such that the n-type chemiresistors and the p-type chemiresistors are in a grouped or segregated arrangement. Referring, for example, to a non-limiting embodiment shown in FIG. 1, sensors 106a- 106r are positioned on a surface of substrate 104 such that sensors 106a- 106i are n-type chemiresistors and sensors 106j-106r are p-type chemiresistors (or vice versa, i.e., such that sensors 106a- 106i are p-type chemiresistors and sensors 106j-106r are n-type chemiresistors). In yet other embodiments, the sensors (e.g., chemiresistors) are positioned on a surface of a substrate such that the n-type chemiresistors and the p-type chemiresistors are in a random arrangement.

[0088] In some embodiments, the sensor array is configured such that exposure to a target analyte results in a negative change in electrical resistance of at least a portion of the plurality of n-type chemiresistors. As described herein in greater detail, for example, the target analyte may comprise a reducing species that donates electrons to at least a portion of the n-type chemiresistors, thereby resulting in an increase in the electron concentration of at least the portion of the n-type chemiresistors, an increase in the electrical conductivity of at least the portion of the n-type chemiresistors, and a decrease in the electrical resistance of at least the portion of the n-type chemiresistors. According to some embodiments, as the electrical resistance of at least the portion of the n-type chemiresistors changes, one or more electrodes in electrical communication with the n-type chemiresistors may capture and transmit a resulting electrical signal for processing, as described herein in greater detail.

[0089] According to certain embodiments, the sensor array is configured such that exposure to a target analyte results in a positive change in electrical resistance of at least a portion of the plurality of p-type chemiresistors. For example, as described herein in greater detail, the target analyte may comprise a reducing species that donates electrons to at least a portion of the p-type chemiresistors, thereby resulting in a decrease in the hole concentration of at least the portion of the p-type chemiresistors, a decrease in the electrical conductivity of at least the portion of the p- type chemiresistors, and an increase in the electrical resistance of the at least the portion of the p-type chemiresistors. In certain embodiments, as the electrical resistance of at least the portion of the p-type chemiresistors changes, one or more electrodes in electrical communication the p- type chemiresistors may capture and transmit a resulting electrical signal for processing, as described herein in greater detail.

[0090] According to certain embodiments, an output of the sensor array provides a signal pattern. In some embodiments, the signal pattern is based on a change or changes in electrical resistance (e.g., an individual change in electrical resistance) of at least 2 sensors (e.g., chemiresistors) (e.g., at least 5 sensors, at least 10 sensors, at least 20 sensors, at least 50 sensors, etc.). In some embodiments, the signal pattern is based on a change or changes in electrical resistance (e.g., an individual change in electrical resistance) of each sensor (e.g., chemiresistor) of the plurality.

[0091] The signal pattern may, in some embodiments, comprise a signal or signals corresponding to the negative change in electrical resistance (e.g., of at least a portion of the n- type chemiresistors) and / or the positive change in electrical resistance (e.g., of at least a portion of the p-type chemiresistors). For example, in certain embodiments, the signal pattern comprises one or more signal areas corresponding to the negative change in electrical resistance (e.g., of at least a portion of the n-type chemiresistors) and / or the positive change in electrical resistance (e.g., of at least a portion of the p-type chemiresistors).

[0092] In certain embodiments, the signal pattern comprises a continuous linear baseline where a negative change in electrical resistance (e.g., of at least a portion of the n-type chemiresistors) and a positive change in electrical resistance (e.g., of at least a portion of the p-type chemiresistors) cancel each other out. In some embodiments, the continuous linear baseline is an uninterrupted line connecting two points on the pattern. The uninterrupted line may, in some embodiments, connect values or points on the signal pattern across a range (e.g., as compared to a discrete point that represents a single data value at a specific location). For example, in certain embodiments, a signal intensity (e.g., magnitude) of a negative change in electrical resistance of at least one n-type chemiresistor (e.g., at least some of the n-type chemiresistors) is substantially equal (or equal) to a signal intensity (e.g., magnitude) of a positive change in electrical resistance of at least one p-type chemiresistor (e.g., at least some of the p-type chemiresistors), which is represented in the signal pattern as a continuous zero-point baseline where the sum of the electrical resistances of the at least one n-type chemiresistor and the at least one p-type chemiresistor is substantially zero (or zero). The signal pattern may, in certain embodiments, comprise more than one continuous linear baseline (e.g., two continuous linear baselines, three continuous linear baselines, etc.).

[0093] In some embodiments, the signal pattern comprises a signal area corresponding to a negative change in electrical resistance (e.g., of at least a first portion of the n-type chemiresistors), a signal area corresponding to a positive change in electrical resistance (e.g., of at least a first portion of the p-type chemiresistors), and a continuous linear baseline where a negative change in electrical resistance (e.g., of at least a second portion of the n-type chemiresistors) and a positive change in electrical resistance (e.g., of at least a second portion of the p-type chemiresistors) cancel each other out. The continuous linear baseline may, in some embodiments, be adjacent to the signal area corresponding to the negative change in electrical resistance (e.g., of at least the first portion of the n-type chemiresistors) and / or the signal area corresponding to the positive change in electrical resistance (e.g., of at least the first portion of the p-type chemiresistors).

[0094] According to certain embodiments, the signal pattern is unique to the composition of the target analyte. In some embodiments, for example, the continuous linear baseline of the signal pattern is unique to the composition of the target analyte and independent of the concentration of the target analyte. In certain embodiments, a signal area corresponding to a negative change in electrical resistance (e.g., of at least a first portion of the n-type chemiresistors), a signal area corresponding to a positive change in electrical resistance (e.g., of at least a first portion of the p- type chemiresistors), and / or the continuous linear baseline where a negative change in electrical resistance (e.g., of at least a second portion of the n-type chemiresistors) and a positive change in electrical resistance (e.g., of at least a second portion of the p-type chemiresistors) cancel each other out differs between each target analyte, thereby providing distinctive signal patterns (e.g., distinctive continuous linear baselines) unique to each target analyte (e.g., a fingerprint). The composition of the target analyte may be detected, in some embodiments, based on an identification of the signal pattern (e.g., based on the continuous linear baseline of the signal pattern).

[0095] In some embodiments, the signal pattern is unique to the concentration of the target analyte. In certain embodiments, for example, the signal pattern comprises one or more contours (e.g., a plurality of contours) having a signal intensity value corresponding to the concentration of the target analyte. In some embodiments, a signal area corresponding to a negative change in electrical resistance (e.g., of at least a portion of n-type chemiresistors) and / or a signal area corresponding to a positive change in electrical resistance (e.g., of at least a portion of p-type chemiresistors) comprises the one or more contours having a signal intensity value corresponding to the concentration of the target analyte. In certain embodiments, the concentration of the target analyte is directly proportional to the signal intensity of the at least one contour. The concentration of the target analyte may be detected, in certain embodiments, based on the at least one contour (e.g., based on the signal intensity of the at least one contour).

[0096] According to some embodiments, at least a portion of the sensors (e.g., n-type chemiresistors and / or p-type chemiresistors) are or comprise an alloy (e.g., a bimetallic alloy, a bimetallic alloy). For example, referring to FIG. 1, at least a portion of sensors 106 (e.g., n-type chemiresistors and / or p-type chemiresistors) are or comprise an alloy. In some embodiments, at least a portion of the n-type chemiresistors are or comprise an alloy. In certain embodiments, at least a portion of the p-type chemiresistors are or comprise an alloy.

[0097] In certain embodiments, at least a portion of the sensors (e.g., n-type chemiresistors and / or p-type chemiresistors) are or comprise a MOF (e.g., a single metallic MOF, a bimetallic MOF, a bimetallic MOF). Referring, for example, to FIG. 1, at least a portion of sensors 106 (e.g., n-type chemiresistors and / or p-type chemiresistors) are or comprise a MOF. In some embodiments, for example, at least a portion of the n-type chemiresistors are or comprise a MOF. In certain embodiments, at least a portion of the p-type chemiresistors are or comprise a MOE Suitable examples of MOFs are described herein in greater detail (e.g., a MOF having the formula shown in Formula (I)).

[0098] In certain non-limiting embodiments, a n-type chemiresistor comprises a MOF of the formula [Ni3(Li)(L2)]n, [NixCuy(Li)(L2)]n, and / or [Cu3(Li)(L2)]n, wherein Li, L2, x, y, and n are defined according to Formula (I). In certain embodiments, a n-type chemiresistor comprises a MOF of Formula (I) wherein M, M’, and M” are each independently selected from the group consisting of a Co metal ion (e.g., Co2+, Co3+), a Ni metal ion (e.g., Ni2+), and a Cu metal ion (e.g., Cu+, Cu2+), provided that each of M, M’, and M” are different metal ions, and wherein each of x, y, and z are greater than 0.

[0099] In some non-limiting embodiments, a p-type chemiresistor comprises a MOF of the formula [Co3(Li)(L2)]n, [CoxCuy(Li)(L2)]n, and / or [CoxNiy(Li)(L2)]n, wherein Li, L2, x, y, and n are defined according to Formula (I). In certain embodiments, a p-type chemiresistor comprises a MOF of Formula (I) wherein M, M’, and M” are each independently selected from the group consisting of a Co metal ion (e.g., Co2+, Co3+), a Ni metal ion (e.g., Ni2+), and a Cu metal ion (e.g., Cu+, Cu2+), provided that each of M, M’, and M” are different metal ions, and wherein each of x, y, and z are greater than 0.

[0100] According to some embodiments, at least one sensor (e.g., n-type chemiresistor and / or p- type chemiresistor) of the plurality (e.g., each sensor of the plurality) may be conductive. At least one sensor of the plurality (e.g., each sensor of the plurality) may have any of a variety of suitable conductivities. In certain embodiments, for example, at least one sensor of the plurality has an electrical conductivity greater than or equal to IO40S / m, greater than or equal to 10'9S / m, greater than or equal to 10'8S / m, greater than or equal to 10'7S / m, greater than or equal to 10'6S / m, greater than or equal to 10'5S / m, greater than or equal to 10'4S / m, greater than or equal to 10'3S / m, greater than or equal to 10'2S / m, greater than or equal to 10 S / m, greater than or equal to 1 S / m, greater than or equal to 10 S / m, greater than or equal to 102S / m, greater than or equal to 103S / m, or greater. In some embodiments, at least one sensor of the plurality has an electrical conductivity less than or equal to 104S / m, less than or equal to 103S / m, less than or equal to 102S / m, less than or equal to 10 S / m, less than or equal to 1 S / m, less than or equal to 104S / m, less than or equal to 10'2S / m, less than or equal to 10'3S / m, less than or equal to IO"4S / m, less than or equal to 10'5S / m, less than or equal to 10'6S / m, less than or equal to 10’7S / m, less than or equal to 10'8S / m, or less than or equal to 10'9S / m. Combinations of the above recited ranges are also possible (e.g., at least one sensor of the plurality has an electrical conductivity greater than or equal to IO0S / m and less than or equal to 104S / m, at least one sensor of the plurality has an electrical conductivity greater than or equal to 10'4S / m and less than or equal to 10'3S / m). Other ranges are also possible.

[0101] According to certain embodiments, the electrical conductivity of a sensor is determined using a four-point probe method.

[0102] In certain embodiments, at least one sensor (e.g., n-type chemiresistor and / or p-type chemiresistor) of the plurality (e.g., each sensor of the plurality) is at least partially porous. An at least partially porous sensor advantageously allows the sensor to absorb one or more gases (e.g., within one or more pores of the sensor). At least one sensor of the plurality (e.g., each sensor of the plurality) may have any of a variety of suitable porosities. In some embodiments, for example, at least one sensor of the plurality has a BET surface area greater than or equal to 500 m2 / g, greater than or equal to 1000 m2 / g, greater than or equal to 1500 m2 / g, greater than or equal to 2000 m2 / g, or greater than or equal to 2500 m2 / g. In some embodiments, at least one sensor of the plurality has a sensor surface area less than or equal to 3000 m2 / g, less than or equal to 2500 m2 / g, less than or equal to 2000 m2 / g, less than or equal to 1500 m2 / g, or less than or equal to 1000 m2 / g. Combinations of the above recited ranges are also possible (e.g., at least one sensor of the plurality has a sensor surface area greater than or equal to 500 m2 / g and less than or equal to 3000 m2 / g, at least one sensor of the plurality has a sensor surface area greater than or equal to 1500 m2 / g and less than or equal to 2000 m2 / g). Other ranges are also possible.

[0103] According to certain embodiments, the BET surface area of a sensor is determined using a BET analyzer.

[0104] Although FIG. 1 shows a sensor array comprising 18 sensors (e.g., sensors 106a-106r), the sensor array may comprise any of a variety of suitable number of sensors (e.g., chemiresistors). In certain embodiments, for example, the sensor array comprises greater than 2 sensors, greater than or equal to 5 sensors, greater than or equal to 10 sensors, greater than or equal 20 sensors, greater than or equal to 50 sensors, greater than or equal to 100 sensors, greater than or equal to 200 sensors, greater than or equal to 500 sensors, greater than or equal to 1,000 sensors, greater than or equal to 5,000 sensors, greater than or equal to 10,000 sensors, greater than or equal to 50,000 sensors, greater than or equal to 100,000 sensors, greater than or equal to 250,000 sensors, greater than or equal to 500,000 sensors, greater than or equal to 1,000,000 sensors, or more. In some embodiments, the plurality of sensors comprises less than or equal to 1,000,000 sensors, less than or equal to 500,000 sensors, less than or equal to 250,000 sensors, less than or equal to 100,000 sensors, less than or equal to 50,000 sensors, less than or equal to 10,000 sensors, less than or equal to 5,000 sensors, less than or equal to 1,000 sensors, less than or equal to 500 sensors, less than or equal to 200 sensors, less than or equal to 100 sensors, less than or equal to 50 sensors, less than or equal to 20 sensors, less than or equal to 10 sensors, or less than or equal to 5 sensors. Combinations of the above recited ranges are possible (e.g., the plurality of sensors comprises greater than or equal to 2 sensors and less than or equal to 1,000,000 sensors, the plurality of sensors comprises greater than or equal to 500 sensors and less than or equal to 1,000 sensors). Other ranges are also possible.

[0105] The substrate (e.g., substrate 104 shown in FIG. 1) may comprise any of a variety of suitable materials. In certain embodiments, for example, the substrate comprises silicon (Si), silicon dioxide (SiO2), glass, alumina (AI2O3), a polymer (e.g., a polyimide, polyethylene terephthalate), a metal, and / or combinations thereof. Other substrate materials are also possible.

[0106] Although not shown in FIG. 1, the sensor array may comprise one or more electrodes. In certain embodiments, for example, the sensor array comprises one or more interdigitated electrodes (IDEs). According to certain embodiments, the plurality of sensors (e.g., chemiresistors) may be in electrical communication with the one or more electrodes. In some embodiments, for example, at least a portion of each sensor is in direct contact with the one or more electrodes. In some embodiments, each sensor is in direct contact with an individual electrode. The one or more electrodes may comprise any of a variety of suitable materials. In some embodiments, for example, the one or more electrodes comprise a metal (e.g., gold, platinum, aluminum), carbon, and / or combinations thereof. Other electrode materials are also possible.

[0107] According to some embodiments, the sensor array is fabricated by depositing the one or more electrodes on the surface of the substrate and depositing the plurality of sensors (e.g., chemiresistors) on the surface of the substrate such that the plurality of sensors is in electrical communication with the one or more electrodes. In some embodiments, depositing the one or more electrodes and / or the plurality of sensors comprises drop-casting, spin-coating, inkjet printing, vapor depositing, and / or combinations thereof. Other deposition methods are also possible.

[0108] The sensor array may comprise (and / or be in wired and / or wireless electrical communication with) one or more additional components not shown in FIG. 1. For example, in certain embodiments, the sensor array comprises (and / or is in wired and / or wireless electrical communication with) circuitry and / or electronics for signal conditioning, readout, and / or output, such as one or more multiplexers, analog-to -digital converters, bridge circuits, and / or microcontrollers. In some embodiments, the sensor array comprises (and / or is in wired and / or wireless electrical communication with) one or more data acquisition and / or processing units, which may be coupled to the circuitry and / or electronics. In certain embodiments, the one or more data acquisition and / or processing units may be configured to receive a readout and / or output from the sensor array and execute data processing of the readout and / or output based on instructions (e.g., memory storing instructions).

[0109] According to certain embodiments, the sensor array may be housed in a housing and / or package that allows controlled exposure to a sample (e.g., a sample suspected of containing an analyte), while advantageously protecting the plurality of sensors (and / or the one or more additional components, such as the circuitry and / or electronics). In some embodiments, the sensor array (and / or the housing and / or package housing the sensor array) comprises one or more fluid (e.g., gas) flow controllers, pre-concentrators, membranes, filters, temperature sensors, and / or humidity sensors.

[0110] According to some embodiments, a method of sensing an analyte is described. In some embodiments, the method comprises exposing a sensor array comprising a plurality of sensors (e.g., chemiresistors) to a sample suspected of containing an analyte. FIGS. 2A-2B show topview schematic diagrams representing a method of exposing sensor array 102 to sample 202 suspected of containing an analyte, in accordance with certain embodiments. According to some embodiments, the sample suspected of containing the analyte flows over a surface of the substrate such that the sample contacts at least one sensor of the sensor array. In some embodiments, the sample contacts each sensor of the sensor array. Referring, for example, to FIGS. 2A-2B, sample 202 suspected of containing an analyte flows over a surface of substrate 104 such that sample 202 contacts at least one sensor 106 (e.g., each sensor 106a-106r) of sensor array 102. According to some embodiments, the exposing is performed continuously such that a sample suspected of containing an analyte continuously flows over a surface of the substrate such that the sample continuously contacts at least one sensor of the sensor array. In some embodiments, the exposing is performed at room temperature (e.g., between 20-25 °C).

[0111] In some embodiments, the method comprises measuring (e.g., individually measuring) a change or changes in electrical resistance of at least 2 sensors (e.g., chemiresistors) (e.g., at least 5 sensors, at least 10 sensors, at least 20 sensors, at least 50 sensors, etc.). In certain embodiments, the method comprises measuring (e.g., individually measuring) a change or changes in electrical resistance of each sensor of the plurality. According to certain embodiments, the change or changes in electrical resistance of the sensors is measured (e.g., individually measured) by applying an electrical stimulus, such as a constant voltage and / or constant current, across the sensor array and recording the resulting electrical response of the sensors over time. In certain embodiments, the electrical resistance of the sensors may be calculated using Ohm’s Law based on the resulting electrical response (e.g., the measured current and / or measured voltage). According to certain embodiments, the method comprises continuously measuring a change or changes in electrical resistance of at least 2 sensors (e.g., each sensor) of the plurality.

[0112] In some embodiments, the measuring comprises measuring a negative change in electrical resistance (e.g., of at least one n-type chemiresistor). For example, as described herein in greater detail, at least a portion of the plurality of sensors (e.g., chemiresistors) are or comprise n-type chemiresistors that produce a negative change in electrical resistance upon exposure to a target analyte. According to some embodiments, the response signal (Sn) of the negative change in electrical resistance (e.g., of the at least one n-type chemiresistor) is calculated as:

[0113] (Rs — Ra) / Rs, wherein:

[0114] Rsis the electrical resistance of the chemiresistor (e.g., the at least one n-type chemiresistor) in the presence of the sample; and

[0115] Rais the electrical resistance of the chemiresistor in the presence of air (i.e., the baseline electrical resistance of the chemiresistor).

[0116] In certain embodiments, the measuring comprises measuring a positive change in electrical resistance (e.g., of at least one p-type chemiresistor). For example, as described herein in greater detail, at least a portion of the plurality of sensors (e.g., chemiresistors) are or comprise p-type chemiresistors that produce a positive change in electrical resistance upon exposure to a target analyte. According to some embodiments, the response signal (Sp) of the positive change in electrical resistance (e.g., of the at least one p-type chemiresistor) is calculated as:

[0117] (Rs — Ra) / Ra, wherein:

[0118] Rsis the electrical resistance of the chemiresistor (e.g., the at least one p-type chemiresistor) in the presence of the sample; and

[0119] Rais the electrical resistance of the chemiresistor (e.g., the at least one p-type chemiresistor) in the presence of air (i.e., the baseline electrical resistance of the chemiresistor).

[0120] In accordance with certain embodiments, the method comprises outputting a signal pattern. In some embodiments, the signal pattern is based on the change or changes in electrical resistance (e.g., the individual change in electrical resistance) of at least 2 sensors (e.g., chemiresistors) (e.g., at least 5 sensors, at least 10 sensors, at least 20 sensors, at least 50 sensors, etc.). In certain embodiments, the signal pattern is based on the change or changes in electrical resistance (e.g., the individual change in electrical resistance) of each sensor (e.g., chemiresistor) of the plurality. In some embodiments, the method comprises continuously outputting a signal pattern.

[0121] The signal pattern may, in some embodiments, comprise a signal corresponding to the negative change in electrical resistance (e.g., of one or more n-type chemiresistors) and / or the positive change in electrical resistance (e.g., of one or more p-type chemiresistors). For example, as described herein in greater detail, the signal pattern may comprise one or more signal areas corresponding to the negative change in electrical resistance (e.g., of one or more n- type chemiresistors) and / or one or more signal areas corresponding to the positive change in electrical resistance (e.g., of one or more p-type chemiresistors).

[0122] In certain embodiments, as described herein in greater detail, the signal pattern comprises a continuous linear baseline (e.g., an uninterrupted line connecting two points on the pattern) where a negative change in electrical resistance (e.g., of one or more n-type chemiresistors) and a positive change in electrical resistance (e.g., of one or more p-type chemiresistors) cancel each other out. For example, a signal intensity (e.g., magnitude) of a negative change in electrical resistance of one or more n-type chemiresistors may be substantially equal (or equal) to a signal intensity (e.g., magnitude) of a positive change in electrical resistance of one or more p-type chemiresistors, which is represented in the signal pattern as a continuous zero-point baseline where the sum of electrical resistances of the one or more n-type chemiresistors and the one or more p-type chemiresistors is substantially zero (or zero). The signal pattern may, in certain embodiments, comprise more than one continuous linear baseline (e.g., two continuous linear baselines, three continuous linear baselines, etc.).

[0123] According to some embodiments, the signal pattern comprises a signal area corresponding to a negative change in electrical resistance (e.g., of one or more n-type chemiresistors), a signal area corresponding to a positive change in electrical resistance (e.g., of one or more p-type chemiresistors), and a continuous linear baseline where at least a portion of the one or more negative changes in electrical resistance and a least a portion of the one or more positive changes in electrical resistance cancel each other out. In some embodiments, the continuous linear baseline is adjacent to the signal area corresponding to the negative change in electrical resistance (e.g., of the one or more n-type chemiresistors) and / or the signal area corresponding to the positive change in electrical resistance (e.g., of the one or more p-type chemiresistors). According to some embodiments, exposing the sensor array to the sample of suspected of containing then analyte, measuring the change in electrical resistance of each sensor of the plurality, and outputting the signal pattern are performed continuously.

[0124] In certain embodiments, the method comprises determining a composition of the target analyte, if present, based on the signal pattern. As described herein in greater detail, for example, the signal pattern may be unique to the target analyte based at least in part on the continuous linear baseline. In some embodiments, a signal area corresponding to a negative change in electrical resistance (e.g., of one or more n-type chemiresistors), a signal area corresponding to a positive change in electrical resistance (e.g., of one or more p-type chemiresistors), and / or the continuous linear baseline where at least a portion of one or more negative changes in electrical resistance and a least a portion of the one or more positive changes in electrical resistance cancel each other out differs between each target analyte, thereby providing distinctive signal patterns (e.g., distinctive continuous linear baselines) unique to each target analyte (e.g., a fingerprint).

[0125] In some embodiments, the method comprises determining a concentration of the target analyte, if present, based on the signal pattern. In some embodiments, as described herein in greater detail, the signal pattern comprises one or more contours (e.g., a plurality of contours) having a signal intensity value corresponding to the concentration of the target analyte. In certain embodiments, a signal area corresponding to a negative change in electrical resistance (e.g., of one or more n-type chemiresistors) and / or a signal area corresponding to a positive change in electrical resistance (e.g., of one or more p-type chemiresistors) comprises the one or more contours having a signal intensity value corresponding to the concentration of the target analyte. In certain embodiments, the concentration of the target analyte is directly proportional to the signal intensity of the one or more contours. The method may, in some embodiments, comprise determining the concentration of the target analyte, if present, based on the signal intensity of the one or more contours.

[0126] According to some embodiments, the method comprises determining a composition and a concentration of the target analyte, if present, based on the signal pattern. For example, in some embodiments, the method comprises: (i) determining a composition of the target analyte based on the continuous linear baseline where at least a portion of one or more negative changes in electrical resistance and a least a portion of one or more positive changes in electrical resistance cancel each other out; and (ii) determining a concentration of the target analyte based on an intensity of at least one contour of the signal pattern. According to certain embodiments, the sample comprises a mixture of substances. In some embodiments, the sample comprises a mixture of fluids (e.g., a mixture of gases, a mixture of liquids, a mixture of gases and liquids).

[0127] The mixture of substances may have any of a variety of suitable relative humidities. For example, in certain embodiments, the mixture of substances has a relative humidity greater than or equal to 10% RH, greater than or equal to 20% RH, greater than or equal to 30% RH, greater than or equal to 40% RH, greater than or equal to 50% RH, greater than or equal to 60% RH, or greater than or equal to 70% RH. In certain embodiments, the mixture of substances has a relative humidity less than or equal to 80% RH, less than or equal to 70% RH, less than or equal to 60% RH, less than or equal to 50% RH, less than or equal to 40% RH, less than or equal to 30% RH, or less than or equal to 20% RH. Combinations of the above recited ranges are possible (e.g., the mixture of substances has a relative humidity greater than or equal to 10% RH and less than or equal to 80% RH, the mixture of substances has a relative humidity greater than or equal to 40% RH and less than or equal to 60% RH). Other ranges are also possible.

[0128] In some embodiments, the relative humidity of the mixture of substances is measured by a hygrometer.

[0129] In some embodiments, the analyte is a reducing species. As described herein in greater detail, a reducing species may donate electrons to a n-type chemiresistor, which results in an increase in electron concentration of the n-type chemiresistor and decrease in electrical resistance of the n-type chemiresistor. In certain embodiments, the reducing species donates electrons to a p-type chemiresistor, which results in a decrease in the hole concentration of the p- type chemiresistor and an increase in the electrical resistance of the p-type semiconductor.

[0130] In certain embodiments, the analyte is an oxidizing species. As described herein in greater detail, an oxidizing species may accept electrons from a n-type chemiresistor, which results in a decrease in electron concentration of the n-type chemiresistor and an increase in electrical resistance of the n-type chemiresistor. In some embodiments, the oxidizing species accepts electrons from a p-type chemiresistor, which results in an increase in the hole concentration of the p-type chemiresistor and an increase in the electrical resistance of the p-type semiconductor.

[0131] The analyte may be any of a variety of suitable analytes. In some embodiments, the analyte comprises a fluid (e.g., a gas, a liquid). In certain embodiments, the analyte comprises a gas. According to some embodiments, the analyte comprises an alcohol, an aromatic, and / or amine. The alcohol, aromatic, and / or amine may, in some embodiments, be a reducing species. In certain embodiments, the analyte comprises methanol, ethanol, propanol, butanol, benzene, toluene, xylene, trimethylamine, hydrogen, methane, isoamyl alcohol, and / or combinations thereof. Other analytes are also possible.

[0132] According to certain embodiments, outputting the signal pattern, determining the composition of the target analyte based on the signal pattern, and / or determining the concentration of the target analyte based on the signal pattern are executed by one or more data acquisition and / or processing units associated with the sensor array. In some embodiments, for example, the method comprises executing instructions (e.g., non-transitory computer-readable medium storing instructions) using one or more data acquisition and / or processing units associated with the sensor array to output the signal pattern, determine the composition of the target analyte based on the signal pattern, and / or determine the concentration of the target analyte based on the signal pattern. In certain embodiments, the instructions (e.g., non-transitory computer-readable medium storing instructions) include a Convolutional Neural Network (CNN) machine learning model, such as a CNN - Long Short-Term Memory (CNN-LSTM) machine learning model. Other non-transitory computer-readable medium storing instructions are also possible.

[0133] Gas sensors are receiving significant attention in the market, with an expected compound annual growth rate of 9.5% from 2023 to 2030. As sensors become miniaturized and energyefficient, and as individual devices become interconnected through the Internet of Things (loT), advancements in computing technology and machine learning algorithms are driving the expanded use of gas sensors in combination with smart devices. Sensors are now being applied in emerging fields such as smart farming, personal healthcare, and environmental air quality monitoring by several global companies. For example, Sensirion AG has launched smart speakers that can warn about indoor air quality, and SIEMENS is making efforts to provide solutions for controlled environment agriculture with integrated hardware and software techniques.

[0134] Fingerprint recognition technology is a highly precise method that utilizes recognizable image patterns such as loops, whorls, and arches formed by ridges. To acquire similar continuous signal patterns from sensor arrays, it is advantageous to implement a continuous composition system. Although gradually changing the metal composition is a good approach, conventional chemiresistors like metal oxides undergo phase transitions when the metal composition changes, resulting in discontinuous physical properties. In contrast, as described herein, electrically conductive metal-organic frameworks (cMOFs) such as M3HITP2 (M = Co, Ni, Cu; HITP = 2,3,6,7,10,11-hexaiminotriphenylene) form a continuous alloys system with a single phase and enable chemiresistive sensing at room temperature, according to certain embodiments. In some embodiments, within the single-phase ternary system, compositional variations induce continuous changes in electrical signals, and the response patterns of alloys effectively create a 'fingerprint' for individual chemicals.

[0135] This disclosure, in some embodiments, describes MOFs, including MOF alloys, where the arrangement can, optionally, involve either or both of the following: (i) each single-metal MOF has sufficient conductivity to allow for resistance measurement, ensuring that the alloy composition can be measured; and / or (ii) all material compositions maintain phase integrity to ensure continuous physical properties. In certain embodiments, the above material design strategies ensure a recognizable continuous chemiresistive response signal pattern.

[0136] U.S. Provisional Patent Application No. 63 / 667,338, filed July 3, 2024, and entitled “Multi-Site Sensor Arrays and Related Methods,” is incorporated herein by reference in its entirety for all purposes.

[0137] The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention.

[0138] EXAMPLE 1

[0139] Fabrication of one-chip devices using cMOF alloy combinations

[0140] To produce continuous M3HITP2 alloy phases, synthetic methods were standardized to maintain a consistent molar ratio of metals to ligands at 3:2 (FIG. 3A). By preparing metal solutions with varying ratios of Co, Ni, and Cu salts, the desired compositions were achieved and a ternary phase diagram with 28 different MOF compositions was successfully organized (FIG. 3B). All materials exhibited consistent crystalline X-ray diffraction (XRD) patterns, confirming that the M3HITP2 MOFs formed alloys without phase segregation. The XRD patterns of M3(HITP)2 (M = Co, Ni, Cu) is exemplified in FIG. 3C. As further evidence of material continuity, the (100) peak position varied slightly depending on the metal type, showing a continuous shift in peak position across the alloy phase (FIG. 3D). In FIG. 3D, the dotted line generally represents the trend from 4.835 to 4.469 shown in the legend. Thus, the ternary phase diagram includes compositions ranging from single-metallic MOFs (vertex) to bimetallic (side) and trimetallic (face) MOF alloys.

[0141] Experimental data supporting gas fingerprinting technique

[0142] To investigate sensing properties, one-chip array devices capable of simultaneously measuring signals from 28 distinct MOF chemiresistors were prepared. The chips featured 28 interdigitated electrodes (IDEs) with a 10 pm gap, arranged within a 10 mm x 10 mm central area of the substrates. The chips were placed in a 3D-printed gas chamber connected to a data acquisition system for real-time gas detection. This setup ensured uniform gas exposure to the MOF arrays and aided in stable data processing (FIG. 4A). Introduction of analytes into the gas chamber varied the resistance of individual chemiresistors in array. When analytes were introduced into the gas chamber, the resistance of each chemiresistor changed. The response signal (.S') was calculated as (Rg- Ra) / Raor (Rg- Ra) / Rg, depending on whether the resistance change was positive or negative, respectively. Here, Rarepresents the resistance in air, and Rgrepresents the resistance in gas.

[0143] To elucidate the mechanisms behind the appearance of fingerprint patterns, the sensing properties of 100 ppm ethanol were examined (FIGS. 4B-4D). Initially, using single metallic MOFs as in conventional methods, Ni3HITP2 exhibited a negative response signal, while C03HITP2 and CU3HITP2 showed positive response signals (FIG. 4B). In the single metallic system, gas sensitivity and selectivity were generally determined by comparing their mutual responses. However, in the binary MOF alloy system, the responses varied continuously across the entire composition range (FIG. 4C). This variation resulted in a zero-cross point (.S' = 0) at a specific composition where the response transitions from positive to negative. The composition of this zero-cross response (ZCR) point was precisely estimated by identifying the intersection of continuous response variations. This pattern served as a distinct indicator for each analyte. For instance, Coi.762Nii.238HITP2 and Nio.i85Cu2.8isHITP2 acted as point indicators for ethanol gas in the binary MOF system. When expanding the chemiresistor array from a linear binary to a planar ternary system, the ZCR pattern indicator evolved from a point to a linear representation (FIG. 4D), similar to the highly recognizable fingerprinting patterns. Overall, the ternary system presents continuous linear indicators that are suitable for improving accuracy of pattern recognition.

[0144] This approach provided absolute gas selectivity due to its consistent ZCR patterns across varying gas concentrations. For instance, methane showed almost identical patterns in fixed positions within the ternary system regardless of the concentration (2000, 1000, 500, and 250 ppm) (FIGS. 5A-5D). In FIGS. 5A-5D, the dotted lines generally represent a transition from a positive response to a negative response, crossing a continuous ZCR linear baseline. Interestingly, the contour related to the intensity of responses varied depending on the concentrations, indicating that the type of gas can be determined independently of its concentration. In the ternary cMOF alloys system, the type of gas was identified through the patterns (ZCR patterns), and the concentration of the gas was determined through intensity (contour), allowing the separation of these two intertwined factors to obtain an absolute signal. Based on the above principle, unique fingerprint patterns were designated for other airborne chemicals (FIGS. 6A-6K). In FIGS. 6A-6K, the dotted lines generally represent a transition from a positive response to a negative response, crossing a continuous ZCR linear baseline. Additionally, regular changes in these patterns according to the similarities between chemicals (such as alcohols, aromatic rings, etc.) were expected. For example, the ZCR patterns of methanol passed through the middle region of Ni3HITP2 and C03HITP2, but they gradually moved toward the Ni composition side as the number of carbons in the alkyl group increases (FIGS. 6A-6D). These regular pattern variations according to functional groups improve the tunability and predictability of this method, providing statistical data to modify the patterns for accurate gas identifications.

[0145] Machine learning for accurate gas fingerprint recognition

[0146] To classify the target gases with high accuracy, a convolutional neural network (CNN) was employed. Given that the characteristics of the device, or its gas sensing performance, continuously vary with the material composition or with the nodes in fingerprint patterns, it was anticipated that the convolutional filters will most effectively learn the information from adjacent nodes. Learning the data values and their gradients from 28 nodes was expected to reduce inaccuracies arising from device-to-device variation, which is a common issue in most electronic devices, particularly around the ZCR nodes. To this end, half of the measured data was randomly selected as the training dataset, while the remaining half was used as the testing dataset.

[0147] The advantages of the embodiments described herein over conventional sensor arrays include scalability and energy efficiency.

[0148] With respect to scalability, conventional sensor array research typically focuses on specific applications, leading to the statistical functionalization of chemiresistors. These gas sensor arrays face significant difficulty in diversifying the range of target gases, and they require pattern recognition techniques to compare mutual relative patterns due to the non-intuitive nature of the signal patterns. However, the continuous cMOF alloy-based sensor array described herein can distinguish every gas absolutely by designating each gas's unique fingerprint. This approach significantly simplifies the unnecessary computations required for pattern recognition, allowing for highly accurate gas detection. Additionally, it is not limited to targeting specific gases, thereby expanding the scope of gas sensor usage. This strategy could enable the practical use of olfactory sensors in everyday life, which has been challenging until now.

[0149] With respect to energy efficiency, most conventional oxide semiconductor-type gas sensors currently require high temperatures (200-400 °C) or high-energy light sources like ultraviolet (UV) for activation. This not only causes degradation of the material but also leads to the deterioration of surrounding equipment, necessitating additional energy sources (such as batteries or light-emitting diodes (LEDs)), thereby limiting scalability. However, the cMOF- based gas sensors described herein operate entirely at room temperature, eliminating the need for energy consumption for activation. This enables ultra-low power consumption and miniaturization.

[0150] EXAMPLE 2

[0151] The following examples describes single glass classification using machine learning.

[0152] Conventional studies that fabricate gas sensor chips and use supervised machine learning to classify gas types treat every different gas concentration as a separate class for training the model. This is primarily because the sensor response pattern or the normalized response pattern changes nonlinearly with concentration, even within the same gas type, making it difficult for the model to learn invariant features within a gas class. However, this approach is impractical given that the concentration space is continuous. In the approach described herein, especially near the zero-cross response (ZCR), the sensor response shows linearity with respect to concentration. Therefore, when the response pattern is normalized before training, nearly identical patterns are obtained regardless of concentration. This provides the ability to train and test different concentrations of the same gas as a single class, which makes machine learningbased classification much more practical.

[0153] A Convolutional Neural Network - Long Short-Term Memory (CNN-LSTM) model was used to classify five gases - NO2, H2, methane, NH3, and ethanol - with over 99% accuracy. This model combines CNN, which is effective for learning spatial data, with LSTM, which learns sequential data. The model has a structure as follows, but any similar model structure would work similarly:

[0154] {2d convolution layer with (in_channels=l, out_channels=16, kernel_size=3), 2d convolution layer with (in_channels=16, out_channels=32, kernel_size=3), 2d convolution layer with (in_channels=32, out_channels=64, kernel_size=3), LSTM layer with (input_size=6400, hidden_size=80, num_layers=2, batch_first=True) Fully connected layer 1 Dropout layer Relu layer

[0155] Fully connected layer 2} The gas concentrations used were as follows: NO2: [0.25, 0.5, 1, 1.5, 2, 3, 2.5, 5 ppm], H2: [250, 500, 1000, 1500, 2000, 3000, 5000 ppm], methane: [250, 500, 1000, 1500, 2000, 3000, 5000 ppm], NH3: [5, 10, 20, 30, 40, 60, 100 ppm] and ethanol: [100, 200, 300, and 400 ppm]. Each gas and concentration was measured 25 times over a period of more than one month. Half of the dataset was used for training and the other half for testing. The model classified both the gas type and its concentration, and it achieved over 90% accuracy.

[0156] EXAMPLE 3

[0157] The following examples describes the analytical decomposition of a gas mixture.

[0158] It has been demonstrated that a sensor response pattern for a gas mixture can be decomposed into a linear combination of the sensor response patterns for its individual constituent analytes. When measuring a mixture of two gases, it is not straightforward whether the mixture’s response can be decomposed into a simple function of the two known individual responses. If it is assumed that there is no interaction between the analytes, the decomposition problem essentially reduces to finding a simple solution that minimizes Objective Function, shown in Equation 1 : where S(x)' is the sensor response pattern for the gas mixture, and Sl singieand S2iSingieare the sensor response pattern for the first individual gas analyte and the second individual gas analyte, respectively.

[0159] There are two major sources of nonlinearity that complicate this decomposition: (i) interference effects from multiple target analytes; and (ii) nonlinearity in sensor response with respect to individual gas concentrations.

[0160] Equation 2 describes the reaction dynamics of the sensor’s interaction sites when exposed to gas analytes (for a chemiresistive sensor, it is assumed that the sensor response is linear to the number of occupied interaction sites by gas analytes). This equation does not have a closed-form solution, exhibiting nonlinearity. When this reaction model is reduced from n- gases to just 2-gases (Equation 3), the nonlinearity becomes evident: the differential equation for 9i depends on 02, and vice versa. However, if it is assumed that the sensor has a very large number of independent interaction sites, Equation 3 can be simplified into Equation 4, where the cross-dependence between analytes is effectively eliminated.

[0161] Even after eliminating one major source of nonlinearity, another remains: the nonlinearity of a single gas’ response pattern with respect to its concentration. However, as shown in Example 2, the ZCR data exhibits linearity. This provides the ability to approximate the gas mixture response as a linear combination of the individual response patterns of the two constituent gases.

[0162] By employing these background and ZCR information, gas response patterns were decomposed for a H2 + CH4 mixture into the sum of the H2 pattern and the CH4 pattern at 9 different concentration ratios of mixtures. As shown in FIG. 7, the calculation result was well aligned with the true concentrations.

[0163] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0164] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0165] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0166] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0167] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0168] As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage.

[0169] Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

[0170] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0171] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMSWhat is claimed is:

1. A composition, comprising: a plurality of metal-organic frameworks (MOFs), each MOF of the plurality having a formula [MxM’yM”z(Li)(L2)]n, wherein:M, M’, and M” are each independently a metal ion, wherein each of M, M’, and M” are different metal ions; x, y, and z are each independently greater than or equal to 0 and less than or equal to 3, wherein the sum of x, y, and z is 3;Li and L2 each comprise a ligand and Li and L2 can be the same or different; n is greater than or equal to 2; the plurality of MOFs comprises at least two MOFs having different formulas; and at least one MOF has the formula [MxM’yM”z(Li)(L2)]n wherein each of x, y, and z are greater than 0.

2. The composition of claim 1, wherein each MOF of the plurality has a different formula.

3. The composition of any one of claims 1-2, wherein the plurality of MOFs comprises at least one MOF having the formula [M3(Li)(L2)]n.

4. The composition of claim 3, wherein the plurality of MOFs comprises at least one MOF having the formula [M’3(Li)(L2)]n.

5. The composition of claim 4, wherein the plurality of MOFs comprises at least one MOF having the formula [M”3(Li)(L2)]n.

6. The composition of any one of claims 1-5, wherein Li and L2 each comprise a multidentate ligand and Li and L2 are the same.

7. The composition of claim 6, wherein the multidentate ligand is a ligand comprising at least two sets of ortho-diimine groups arranged about an organic core.

8. The composition of any one of claims 6-7, wherein the multidentate ligand is 2, 3, 6, 7, 10, 11 -hexaimino triphenylene.

9. The composition of any one of claims 1-8, wherein M, M’, and M” are each independently selected from the group consisting of cobalt (Co), nickel (Ni), and copper (Cu).

10. A sensor array, comprising: a plurality of n-type chemiresistors; and a plurality of p-type chemiresistors, wherein the sensor array is configured such that exposure to an analyte results in: (i) a negative change in electrical resistance of at least a portion of the plurality of n-type chemiresistors; and (ii) a positive change in electrical resistance of at least a portion of the plurality of p-type chemiresistors, and wherein an output of the sensor array provides a signal pattern unique to a composition of the analyte, the signal pattern comprising a continuous linear baseline where the negative change in electrical resistance and the positive change in electrical resistance cancel each other out.

11. The sensor array of claim 10, wherein at least a portion of the plurality of n-type chemiresistors and / or at least a portion of the plurality of p-type chemiresistors comprise an alloy.

12. The sensor array of any one of claims 10-11, wherein the plurality of n-type chemiresistors and / or the plurality of p-type chemiresistors comprise a plurality of MOFs.

13. The sensor array of claim 12, wherein the plurality of n-type chemiresistors and / or the plurality of p-type chemiresistors comprise the composition of any one of claims 1-9.

14. A method of sensing an analyte, comprising: exposing the sensor array of any one of claims 10-13 to a sample suspected of containing an analyte; measuring the negative change in electrical resistance and the positive change in electrical resistance; and outputting the signal pattern.

15. The method of claim 14, further comprising determining the composition of the analyte, if present, based on the signal pattern.

16. The method of any one of claims 14-15, wherein the sample comprises a mixture of substances comprising the analyte.

17. The method of any one of claims 14-16, further comprising determining a concentration of the analyte, if present, based on the signal pattern.

18. A method of sensing an analyte, comprising: exposing a sensor array comprising a plurality of chemiresistors to a sample suspected of containing an analyte, wherein the sample comprises a mixture of gases; measuring a change in electrical resistance of at least two chemiresistors of the plurality; outputting a signal pattern based on the change in electrical resistance of the at least two chemiresistors; and determining a composition and a concentration of the analyte, if present, based on the signal pattern.

19. The method of any one of claims 17-18, wherein the signal pattern comprises a plurality of contours.

20. The method of claim 19, wherein a signal intensity of at least one contour of the plurality corresponds to the concentration of the analyte.

21. The method of claim 20, further comprising determining the concentration of the analyte, if present, based on the signal intensity of the at least one contour.

22. The sensor array or method of any one of claims 10-21, wherein the analyte comprises a gas.

23. The sensor array or method of any one of claims 10-22, wherein the analyte comprises an alcohol, an aromatic, and / or an amine.

24. The sensor array or method of any one of claims 10-23, wherein the analyte is selected from the group consisting of methanol, ethanol, propanol, butanol, benzene, toluene, xylene, trimethylamine, hydrogen, methane, and isoamyl alcohol.

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